Schottky barrier diode, which has advantages of fast switching speed and low forward voltage drop, has been used widely for lower power rectifier or detector circuits in high-frequency range. Integrated silicon-based Schottky barrier diode into CMOS RF IC can increase high frequency performance and decrease the production cost and chip size, in particular for fabricating dc voltage generator in a passive RFID chip. Typically, Schottky diode consists of a metal layer connected to a doped semiconductor layer, and the Schottky barrier is formed at the juncture of the metal layer and the semiconductor layer. Breakdown voltage is improved by placing a p-type guard ring in a semiconductor substrate around the Schottky barrier. Traditionally the p-type guard ring is separated from the Schottky barrier by an optimized distance, or in contact with a portion of the Schottky barrier. However, conventional Schottky barrier diodes exhibit higher than desirable leakage current at the reverse bias, causing higher power dissipation and limiting the circuit applications in RFID, charge pump, etc.